Rib muscles and diaphragm contract making the chest cavity?

The correct answer is: larger.

The rib muscles and diaphragm are the primary muscles responsible for breathing. When these muscles contract, they pull the rib cage upward and outward, and the diaphragm moves down, enlarging the chest cavity. This expansion of the chest cavity creates a negative pressure within the lungs, causing air to be drawn in through the nose or mouth.